PUMP UNIT

Abstract

A pump unit includes a housing which has an outwardly open recess, in which a pump is arranged. The recess is closed by a cover. The pump unit also has a pressure relief valve which is arranged in an opening of the housing which opens to the outside. The pressure relief valve has a valve seat which is formed in the opening and against which a seat valve member is loaded in the closing direction by way of a prestressed compression spring. The seat valve member can be loaded in the opening direction by the outlet pressure of the pump.

Description

The invention relates to a pump unit having a housing which has an outwardly open recess, in which a pump is arranged, the recess being closed by a cover, and having a pressure relief valve which is arranged in an opening of the housing which opens to the outside, which pressure relief valve has a valve seat which is formed in the opening and against which a seat valve member is loaded in the closing direction by way of a prestressed compression spring, which seat valve member can be loaded in the opening direction by the outlet pressure of the pump.

It is an object of the invention to provide a pump unit of the type mentioned at the outset, which pump unit has a simpler construction with fewer components and can be assembled more simply.

According to the invention, this object is achieved by virtue of the fact that the recess and the opening, extending parallel to one another on a housing outer wall, open to the outside out of the housing and can be closed by way of a common cover.

As a result of this configuration, both the recess, in which the pump is situated, and the opening for the pressure relief valve can be closed by way of the mounting of one cover.

Here, the cover is of simple construction and can be produced simply if the housing outer wall is planar in the region of the orifices of the recess and the opening.

It likewise leads to a reduction of the components and the assembly outlay if a sealing groove which encloses the orifices of the recess and the opening jointly is formed in the housing outer wall, into which sealing groove an elastic seal of corresponding shape is inserted, against which seal the cover is in contact sealingly in its closed position.

In order to fasten the cover to the housing, the cover can be stressed into contact with the housing outer wall by way of screws which can be screwed into threaded holes in the housing.

Here, the cover can be stressed homogeneously against the housing wall if the cover can be stressed onto the housing outer wall by way of at least two pairs of screws, the connecting lines of the two screw pairs intersecting, in particular, in the middle of the orifice of the recess of the pump.

For exact positioning of the cover and possibly for axial guidance of the pump which is inserted into the recess or part of the pump, the cover can have a guide attachment on its side which faces the housing, which guide attachment corresponds to the cross section of the orifice of the recess and protrudes into the recess.

If the compression spring which loads the seat valve member in the closing direction is supported on the cover, the prestress of the compression spring is also automatically generated by way of the mounting, by the screw pairs stressing the cover against the housing wall.

In order to guide the seat valve member between the open and closed position, the seat valve member can have a coaxial guide shank on its side which faces away from the valve seat, which valve shank is guided displaceably in a guide hole which is formed in the cover.

Here, the guide shank can be configured as a locating shank and the guide hole can be configured as a locating hole for exact guidance.

In order that hydraulic fluid can flow into and out of the free volume in the guide hole behind the guide shank and the seat valve member can move largely freely in the guide hole, the guide shank can have one or more axial grooves on its cylindrical circumferential face in its region which dips into the guide hole.

In order to simplify mounting, the locating hole can have an insertion radius on its orifice.

In a manner which saves installation space and makes it possible to use simple standard components, the compression spring can be a compression coil spring which encloses the locating shank at a radial spacing and is supported with its one end on the seat valve member and with its other end on the cover.

Here, the compression coil spring can be guided with its one end on a cylindrical attachment of the seat valve member and/or with its other end on an annular depression in the cover.

If the valve seat is a conical valve seat and the seat valve member is a conical seat valve member, this leads to reliable closing of the pressure relief valve.

Separate lines to a container for the shut-off hydraulic fluid are not required if the outlet side of the pressure relief valve is connected to the inlet of the pump via a channel which is formed in the housing and/or the cover.

The pump can be a charge pump, the outlet of which is connected to the inlet of a main pump and always reliably supplies the latter with hydraulic fluid, in particular at a pressure between approximately 2 bar and 10 bar above atmospheric pressure.

If the housing of the charge pump can be flange-connected to the main pump here, a compact hydraulic unit is produced.

One exemplary embodiment of the invention is shown in the drawing and will be described in greater detail in the following text.

In the drawing:

FIG. 1 shows a side view of a gerotor pump without a cover,

FIG. 2 shows a section along the line II-II in FIG. 1,

FIG. 3 shows a section along the line III-III in FIG. 1, and

FIG. 4 shows a section along the line IV-IV in FIG. 1.

The gerotor pump which is shown has a housing 1 which is configured as a connecting plate and has a first housing outer wall 2, to which a main pump which is configured, for example, as an axial piston pump can be flange-connected, the suction connector of which is supplied with hydraulic fluid at a charge pressure by the gerotor pump which is configured as a charge pump.

The second housing outer wall 3 of the housing 1 which is parallel to the first housing outer wall 2 is of planar configuration.

A cup-like recess 4 of circular cross section opens to the outside toward said second housing outer wall 3, in which recess 4 an annular external rotor 5 of the gerotor pump is mounted rotatably. The annular external rotor 5 is provided on its radially circumferential inner wall with internal teeth which are in meshing engagement with the external teeth of an internal rotor 6.

Here, the number of internal teeth is greater by at least one than the number of external teeth.

The internal rotor 6 is arranged fixedly on a drive shaft 7 which is mounted rotatably in anti-friction bearings 8 and 9 on both sides of the internal rotor 6 and can be driven rotatably about a rotational axis 21 by a drive (not shown) via the drive shaft of the main pump.

Next to the recess 4, an opening 10 which is configured as a hole is arranged in parallel in the housing 1, which opening 10 likewise opens to the outside toward the second housing outer wall 3.

A sealing groove 11 which encloses the orifices of the recess 4 and the opening 10 jointly is formed in the second housing outer wall 3, into which sealing groove 11 an elastic seal 12 which is configured as a sealant tape of corresponding shape is inserted. A cover 13 is in contact with the second housing outer wall 3 via the seal 12, which cover 13 covers both the orifice of the recess 4 and the orifice of the opening 10 and has a guide attachment 14 which projects toward the housing 1. The cross section of the guide attachment 14 corresponds to that of the recess 4, and said guide attachment 14 protrudes into said recess 4 in such a way that it forms an axial guide for the external rotor 5.

The other axial guide is formed by the bottom 15 of the cup-shaped recess 4.

On one side of the internal rotor 6, the drive shaft 7 protrudes through a bottom-side bearing hole 16 in the housing 1, in which bearing hole 16 the first anti-friction bearing 8 is arranged.

The other end of the drive shaft 7 protrudes into a bearing recess 17 which is not of continuous configuration in the cover 13, in which bearing recess 17 the second anti-friction bearing 9 is inserted, the drive shaft 7 being guided axially by way of the bottom 18 of said bearing recess 17.

The cover 13 can be stressed onto the second housing outer wall 3 by way of the screw heads 20 of four screws 19 which are arranged in the corners of a rectangle. The screws penetrate corresponding holes in the edge region of the cover 13 and holes which are aligned therewith in the housing 1 and can be screwed with their threaded shanks into threaded holes which are formed in a housing part of the main pump.

In each case two screws 19 are arranged so as to lie diametrically opposite one another with regard to the rotational axis 21 of the drive shaft 7.

Two screws 19 can therefore be connected in each case by an imaginary connecting line, the two connecting lines 22 of the two pairs crossing in the rotational axis 21 of the drive shaft 7 (tandem screw connection).

The hole of the opening 10 merges at a spacing from the second housing outer wall 3 into a conical valve seat 23 of a pressure relief valve 32, the valve passage of which can be closed by way of a conical seat valve member 24 which is arranged in the opening 10.

On its side which faces away from the conical valve seat 23, the conical valve seat member 24 has a coaxial locating shank 25 which protrudes with its free end into a locating hole 26 of corresponding cross section which is formed in the cover 13, which locating shank is guided coaxially with respect to the conical valve seat 23 in said locating hole 26.

The locating shank 25 is provided on its inner circumferential face with six axial grooves 27 in a manner distributed uniformly over its circumference.

The opening of the locating hole 26 is provided with an insertion radius 28.

The locating shank 25 is enclosed at a radial spacing by a compression coil spring 29 which is supported with its one end on the cover 13 and is in contact by way of its other end with the conical seat valve member 24 and loads the latter with prestress into its closed position on the conical valve seat 23.

The opening pressure, at which the conical seat valve member 24 lifts up from the conical valve seat 23, is determined by way of the prestress.

Counter to the force of the compression coil spring 29, the conical seat valve member 24 is loaded in the valve opening direction by the outlet pressure of the gerotor pump via a branch 30 of the outlet 31 of the gerotor pump. The outlet channel 31 of the gerotor pump at the same time forms the inlet channel of the main pump.

If the delivery pressure of the gerotor pump rises above the opening pressure of the pressure relief valve 32, the conical seat valve member 24 is lifted up from the conical valve seat 23 and hydraulic fluid can flow out via the opening 10 and a channel 33 which is formed in the housing 1 to an inlet chamber 34 of the gerotor pump, to which inlet chamber 34 a suction connector of the gerotor pump is also connected.

The channel 35 which can be seen in FIG. 3 is the outlet channel of the main pump. The outlet channel 35 and the inlet channel 31 merge into kidney-shaped grooves on the outer wall 2 of the housing 1.

Claims

1. A pump unit, comprising: a housing including an outwardly open recess, a pump arranged in the recess, and the recess closed by a cover; anda pressure relief valve arranged in an opening of the housing, the pressure relief valve configured to open to an outside of the housing, the pressure relief valve including a valve seat formed in the opening, and the valve seat configured such that against the valve seat a seat valve member is loaded in a closing direction by way of a prestressed compression spring, the seat valve member configured to be loaded in an opening direction by an outlet pressure of the pump,wherein the recess and the opening extend parallel to one another on a housing outer wall,wherein the recess and the opening open to the outside out of the housing, andwherein the recess and the opening are configured to be closed by the cover.

2. The pump unit as claimed in claim 1, wherein the housing outer wall is planar in a region of orifices of the recess and the opening.

3. The pump unit as claimed in claim 2, further comprising: a sealing groove configured to enclose the orifices of the recess and the opening jointly, the sealing groove formed in the housing outer wall; andan elastic seal of corresponding shape inserted into the sealing groove,wherein, in a closed position, the cover is in contact sealingly against the elastic seal.

4. The pump unit as claimed in claim 1, wherein the cover is configured to be stressed into contact with the housing outer wall by way of screws configured to be screwed into threaded holes in the housing.

5. The pump unit as claimed in claim 1, wherein the cover includes a guide attachment on a side which faces the housing, the guide attachment configured to correspond to a cross section of the orifice of the recess and to protrude into the recess.

6. The pump unit as claimed in claim 1, wherein the compression spring which loads the seat valve member in the closing direction is supported on the cover.

7. The pump unit as claimed in claim 1, wherein the seat valve member includes a coaxial guide shank on a side which faces away from the valve seat, the guide shank configured to be guided displaceably in a guide hole formed in the cover.

8. The pump unit as claimed in claim 7, wherein the guide shank has at least one axial groove in a cylindrical circumferential face in a region which dips into the guide hole.

9. The pump unit as claimed in claim 6, wherein the compression spring is a compression coil spring configured to enclose the guide shank at a radial spacing and is supported with a first end on the seat valve member and with a second end on the cover.

10. The pump unit as claimed in claim 1, wherein the valve seat is a conical valve seat and the seat valve member is a conical seat valve member.

11. The pump unit as claimed in claim 1, wherein an outlet side of the pressure relief valve is connected to an inlet of the pump via a channel formed in at least one of the housing and the cover.

12. The pump unit as claimed in claim 1, wherein the pump is a charge pump, and an outlet of the charge pump is connected to an inlet of a main pump.

13. The pump unit as claimed in claim 12, wherein the housing of the charge pump is configured to be flange-connected to the main pump.